Fix random string generation

Our variable `alphabet` contains 62 alphanumeric symbols + '\0'.
When we use sizeof(alphabet) we will get 63 due to that.
But we want to choose a random numbers from the 62 alphanumeric letters only.

This mistake caused us to have strings with a max length of `length`
instead of the exact length.

When doing https://github.com/profanity-im/profanity/issues/1520
this caused our algo for muc reflection to not catch since we expect the
random ID to be exactly 15 symbols long in `message_is_sent_by_us()`.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/common.c b/src/common.c
index eca444e6..6020b8c3 100644
--- a/src/common.c
+++ b/src/common.c
@@ -441,13 +441,14 @@ get_random_string(int length)
     GRand* prng;
     char* rand;
     char alphabet[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+    int endrange = sizeof(alphabet) - 1;
 
     rand = calloc(length + 1, sizeof(char));
 
     prng = g_rand_new();
 
     for (int i = 0; i < length; i++) {
-        rand[i] = alphabet[g_rand_int_range(prng, 0, sizeof(alphabet))];
+        rand[i] = alphabet[g_rand_int_range(prng, 0, endrange)];
     }
     g_rand_free(prng);